This invention relates generally to an improved injector device for the placement of a subcutaneous infusion set on a patient. Examples of injector devices for the placement of a subcutaneous infusion set are disclosed in U.S. Pat. Nos. 6,093,172, 5,851,197 and WO 99/33504, incorporated by reference herein.
Medical needles are widely used in the course of patient treatment, particularly for delivery of selected medications. In one form, hollow hypodermic needles are employed for transcutaneous delivery of the medication from a syringe or the like, see U.S. Pat. No. 5,665,071. In another, as shown in U.S. Pat. No. 5,591,188 incorporated herein by reference, an insertion needle used in conjunction with an injector device is employed for transcutaneous placement of a soft and relatively flexible tubular cannula, followed by removal of the insertion needle and subsequent infusion of medical fluid to the patient through the cannula.
It is often necessary for a patient to transcutaneously place the medical needle himself. For example, diabetic patients frequently place a subcutaneous infusion set with a cannula for subsequent programmable delivery of insulin by means of a medication infusion pump. Such subcutaneous infusion sets are disclosed, for example, in U.S. Pat. Nos. 4,755,173, 5,176,662, 5,257,980 and WO 98/58693 which are incorporated by reference herein.
Some patients are reluctant or hesitant to pierce their own skin with a medical needle, and thus encounter difficulties in correct needle placement for proper administration of the medication. Such difficulties can be attributable to insufficient manual skill to achieve proper needle placement or alternately to anxiety associated with anticipated discomfort as the needle pierces the skin. This problem can be especially significant with medications delivered via a subcutaneous infusion set, since incorrect placement can cause kinking of the cannula and resultant obstruction of medication flow to the patient Cannula kinking can be due to infusion set placement at an incorrect angle relative to the patient""s skin, and/or needle placement with an incorrect force and speed of insertion.
The present invention is aimed at providing an improved injector device, which may allow for a shortening of the total time required for the placement of an infusion set. The present invention also aims at providing an improved spring-type drive for urging a plunger within a housing to an advanced position.
In accordance with the invention, an injector device has a plunger with a medical needle, preferably a solid needle incapable of delivering a fluid, and is adapted for the quick and easy transcutaneous placement through the skin of a patient of the cannula of a subcutaneous infusion set, the insertion needle extending through the infusion set and protruding from the end of the cannula. The injector device is designed to place the cannula with the insertion needle extending therethrough with a controlled force and speed of insertion to ensure proper needle placement with minimal patient discomfort. The injector device may also allow placement of the insertion needle through the skin at a selected insertion angle.
Preferably, the injector device is provided to the patient as a sterile sealed, single use assembly including a subcutaneous infusion set with a housing already mounted on the insertion needle of the injector device, thereby reducing the number of components to be handled by the patient prior to the placement of the subcutaneous infusion set.
More particularly, the injector device comprises a device housing having an elongated bore formed therein and a plunger slidably received within the bore for movement between an advanced position and a retracted position, the plunger having substantially non-detachably secured thereto an insertion needle adapted to receive and support said cannula in a position with the cannula oriented for transcutaneous placement upon movement of the plunger with said needle from the retracted position to the advanced position. A drive urges the plunger with a controlled force and speed from the retracted position toward the advanced position to transcutaneously place said cannula of said subcutaneous infusion set received on said insertion needle. The insertion needle on the plunger is removable from said cannula while maintaining the transcutaneous placement of the cannula. By xe2x80x9csubstantially non-detachablyxe2x80x9d as used in the present application is meant a connection, which will remain stable under normal conditions of use to allow the needle to remain on the plunger when retracting the injector device from a patient""s skin.
Preferably, the injector comprises a spring-loaded plunger having a head for receiving the infusion set in a position with the insertion needle projecting outwardly for transcutaneous placement through the skin of a patient. A front end of the housing is designed for pressed placement against the skin of a patient, at a selected needle insertion site, and in an orientation with the needle disposed at a correct or desired insertion angle. A trigger member is operable to release the plunger and thereby permit the drive spring to carry the infusion set toward the patient""s skin with a controlled force and speed, resulting in proper transcutaneous placement of the insertion needle with minimal patient discomfort.
The invention also relates to a novel spring-type drive for urging the plunger of an injector device to the advanced position, preferably for transcutaneously placing a subcutaneous infusion set, wherein the drive comprises a number of individual, elongated flexible plastics members, preferably extending around a respective part of the periphery of the plunger, in the annular space between the plunger and a device housing. Each member is connected with the plunger and with the device housing. In the advanced position of the plunger, the plastics members are essentially plane and non-deformed. However, when moving the plunger to the retracted position, the plastics members are bend, setting up the required force that seeks to drive the plunger to an advanced position. The novel spring-type drive may also be implemented in injector devices of the type disclosed in U.S. Pat. Nos. 6,093,172, 5,851,197 and WO 99/33504 where the plunger head does not have an insertion needle mounted thereon for receiving an infusion set, but includes a recess adapted for receiving as well as supporting a subcutaneous infusion set.